These frameworks provide extensive visualization functionality, but may not meet the needs that arise in the development of custom visualization systems.
Custom visualizations may require visual features or data types
not supported by out-of-the-box solutions, may involve interactive response to user actions that exceed the options provided by these frameworks, and may demand integration of multiple visual facets into a coherent whole. Furthermore, the use of standardized browsers may impose hefty dependencies and inclusion of unwanted GUI components.
To avoid these compromises, developers of custom visualization systems often turn to core web browser technologies (HTML, CSS, SVG, Canvas, WebGL), or libraries that lightly abstract over those core technologies (D3[1]}, PixiJS[2]}).
